Major interaction on record — check this product against your medications before combining. Check your meds →
Dietary supplement

Soy Isoflavones Extract Ingredients & Drug Interactions

by 21st Century

Soy Isoflavones Extract label
See full label image
Capsule Category: Botanical
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Soy Isoflavones Extract against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Major

Soy Isoflavones Extract is a dietary supplement by 21st Century with 1 active ingredient. Its ingredients are commonly taken for menopause symptoms (hot flashes), heart and cholesterol health, bone health.Based on those ingredients, 611 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are Soy Isoflavones Extract, Powder. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Soy Isoflavones Extract by 21st Century

Ask about any prescription or over-the-counter medication and we check it for interactions with Soy Isoflavones Extract by 21st Century — and tell you which ingredient is responsible.

Pharmacist-reviewed data Checks every ingredient Answer in seconds
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HelloPharmacist Scorecard of Soy Isoflavones Extract by 21st Century

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains one active ingredient: soy isoflavones extract, a concentrated powder derived from soy. The remaining ingredients — oat fiber, rice bran, cellulose, silicon dioxide, magnesium silicate, and magnesium stearate — are inactive fillers and binders that make up the capsule.

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: Menopause and bone health support.
  • We looked for evidence on: Menopausal symptoms, Postmenopausal conditions, Osteoporosis, Cardiovascular disease (CVD), Hyperlipidemia, Hot flashes — and 2 related terms.
  • The strongest evidence on file: Soy is rated "Possibly Effective" for Osteoporosis (Natural Medicines).
  • Also on file: Soy is rated "Possibly Effective" for Hyperlipidemia, Menopausal symptoms.
  • Also on file: Soy is rated "Possibly Ineffective" for Breast cancer-related hot flashes.

Soy isoflavones have possibly effective evidence for several uses. The research suggests they may help with blood sugar control in people with diabetes, help lower cholesterol (hyperlipidemia), support bone health in osteoporosis, modestly reduce high blood pressure, and help with diarrhea.

Keep in mind these ratings reflect what the evidence shows so far — they're not guarantees, and results vary from person to person.

The evidence, ingredient by ingredient Soy

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Soy isoflavone supplements are generally well tolerated, though concentrated supplements warrant more caution than soy foods in a normal diet. The most common side effects reported with oral soy are bloating, constipation, diarrhea, and nausea.

Some people can have allergic reactions — skin rash, itching, and in rare cases more serious reactions. There's no established safety data on concentrated isoflavone supplements during pregnancy or breastfeeding; soy foods eaten normally while breastfeeding are fine, but high-dose supplements haven't been well studied.

Talk to your doctor or pharmacist about whether this product is right for you during pregnancy or while nursing.

Side effects, ingredient by ingredient Soy

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Soy.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; diabetes medications.
  • For scale: 611 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this product, check your medications against these types: monoamine oxidase inhibitors (MAOIs), blood pressure medications, blood thinners like warfarin, diabetes drugs, estrogen therapy, thyroid medications like levothyroxine, diuretics (water pills), and caffeine-containing products. All of these are documented to interact with soy isoflavones at varying levels of seriousness.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Major medication interactions have been identified, and safety information is well characterized.

This supplement works best for people managing diabetes, high cholesterol, bone health, or blood pressure — but only if they're not on an MAOI, blood thinner, thyroid medication, or blood pressure drugs without checking first. Anyone on prescription medications should run them through the checker below before starting.

If you're pregnant, nursing, or have a soy allergy, talk to your pharmacist.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Jan 22, 2022.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Soy Isoflavones Extract, straight from the product label.

Brand 21st Century
Barcode (UPC) 740985223062
Net contents 60 Vegetarian Capsule(s)
Market status On market
Date entered into DSLD Jan 22, 2022
DSLD ID 258593
Product type Botanical
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegetarian, Adult Female (18 - 50 Years), Gluten Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Soy Isoflavones Extract by 21st Century, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
2 Vegetarian Capsule(s)
Maximum serving Sizes:
2 Vegetarian Capsule(s)
Servings per container
30
UPC/BARCODE
740985223062
IngredientAmount% DV
Total Carbohydrate1 Gram(s)1%
Soy Isoflavones Extract, Powder100 mg--

Other ingredients: Oat Fiber, Rice Bran, Cellulose, Silicon Dioxide, Magnesium Silicate, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Directions: As an herbal supplement, adults take two (2) capsules daily with any meal or as directed by a healthcare provider. Do not exceed recommended dosage.

Precautions

Do not exceed recommended dosage.

Warning: Consult a healthcare provider prior to use if pregnant, nursing, on medications, have a medical condition or are planning a medical procedure.

Stop use and contact a physician if adverse reactions occur.

Keep out of reach of children.

Do not use if product appears to be tampered with or seal is broken.

Contains soy.

General Statements

Individual results may vary.

Storage

Store at room temperature.

Formulation

No added sugar, salt, yeast, preservatives or artificial flavors.

100% Vegetarian.

Gluten free

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Formula

Standardized Soy Isoflavones Extract

Women's Health Support

Soy Isoflavones support women’s health especially during midlife years.

FDA Statement of Identity

Herbal Supplement

Seals/Symbols

Guaranteed quality Laboratory tested

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Soy Isoflavones Extract by 21st Century label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Soy Isoflavones Extract label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Soy Isoflavones Extract by 21st Century

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size2 Vegetarian Capsule(s) Dosage formCapsule Servings per container30 Amounts shown are per serving.

Soy Isoflavones Extract, Powder

Interacts with
611 drugs
100 mg per serving Form: Isoflavones

Soy is a nutritious bean that is a staple food and a popular source of plant protein and isoflavones. Eating soy foods as part of a balanced diet is g...

Soy Isoflavones Extract, Powder monograph & interactions

Other (inactive) ingredients: Oat Fiber, Rice Bran, Cellulose, Silicon Dioxide, Magnesium Silicate, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Soy Isoflavones Extract by 21st Century Drug Interactions

Want to check YOUR meds against Soy Isoflavones Extract?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
611Drugs
9 Major 343 Moderate 259 Minor

Ingredients driving the most interactions

Soy Isoflavones Extract, Powder 611

Individual Drug Interactions

The ingredients in Soy Isoflavones Extract interact with 611 drugs. Click any drug to see the details.

1 of the 1 ingredient in Soy Isoflavones Extract interact with drugs. Each result below shows which ingredient is responsible. Soy Isoflavones Extract, Powder

Each ingredient & the kinds of drugs it affects

For each ingredient in Soy Isoflavones Extract with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Soy Isoflavones Extract, Powder12 drug types · 611 drugs

Monoamine Oxidase Inhibitors (Maois)

Taking soy products containing high amounts of tyramine along with MAOIs can increase the risk of hypertensive crisis.
Fermented soy products such as tofu and soy sauce contain tyramine, a naturally occurring chemical that affects blood pressure regulation. The metabolism of tyramine is decreased by MAOIs. Consuming more than 6 mg of tyramine while taking an MAOI can increase the risk of hypertensive crisis. The amount of tyramine in fermented soy products is usually less than 0.6 mg per serving; however, there can be significant variation depending on the specific product used, storage conditions, and length of storage. Storing one brand of tofu for a week can increase tyramine content from 0.23 mg to 4.8 mg per serving. Advise patients taking MAOIs to avoid fermented soy products that contain high amounts of tyramine.

Likelihood Likely Evidence C
Antidiabetes Drugs

Soy can lower blood glucose and have additive effects with antidiabetes drugs.
Clinical research shows that whole soy diets and soy-based meals reduce fasting glucose levels in diabetic and non-diabetic individuals. Also, individuals following a soy-based meal replacement plan seem to require lower doses of sulfonylureas and metformin to manage blood glucose levels when compared with individuals following a diet plan recommended by the American Diabetes Association.

Likelihood Possible Evidence A
Antihypertensive Drugs

Theoretically soy protein may have additive effects with antihypertensive drugs and increase the risk of hypotension.
Although some contradictory research exists, most clinical evidence suggests that consuming soy protein modestly reduces systolic and diastolic blood pressure in individuals with prehypertension or hypertension.

Likelihood Possible Evidence A
Caffeine

Theoretically, soy might reduce the clearance of caffeine.
Soy contains genistein. Taking genistein 1 gram daily for 14 days seems to inhibit caffeine clearance and metabolism in healthy females. This effect has been attributed to inhibition of the cytochrome P450 1A2 (CYP1A2) enzyme, which is involved in caffeine metabolism. It is unclear if this effect occurs with the lower amounts of genistein found in soy.

Likelihood Possible Evidence D
Diuretic Drugs

Theoretically, soy might have additive effects when used with diuretic drugs.
Animal research suggests that genistein, a soy isoflavone, increases diuresis within 6 hours of subcutaneous administration in rats. The effects seem to be similar to those of furosemide. This effect has not been reported in humans.

Likelihood Possible Evidence D
Estrogens

Theoretically, soy might competitively inhibit the effects of estrogen replacement therapy.
Soy contains phytoestrogens and has been shown to have estrogenic activity in some patients. Although this has not been demonstrated in humans, theoretically, concomitant use of soy with estrogen replacement therapy might reduce the effects of the estrogen replacement therapy.

Likelihood Possible Evidence D
Levothyroxine (Synthroid, Others)

Soy products might reduce the absorption of levothyroxine in some patients.
Preliminary clinical research and a case report suggest that soy-based formulas inhibit the absorption of levothyroxine in infants with congenital hypothyroidism. A levothyroxine dosage increase may be needed for infants with congenital hypothyroidism while using soy-based formulas, and the dose may need to be reduced when soy-based formulas are no longer administered. However, in postmenopausal adults, clinical research shows that taking a single dose of soy extract containing isoflavones 60 mg along with levothyroxine does not affect the oral bioavailability of levothyroxine.

Likelihood Possible Evidence B
Progesterone

Theoretically, combining soy isoflavones with transdermal progesterone may worsen bone density.
Clinical research suggests that significant bone loss may occur in females with osteoporosis who receive a combination of transdermal progesterone with soy milk containing isoflavones when compared with placebo, soy milk alone, or progesterone alone.

Likelihood Possible Evidence A
Tamoxifen (Nolvadex)

Theoretically, estrogenic soy isoflavones might alter the effects of tamoxifen.
Laboratory research suggests that genistein and daidzen, isoflavones from soy, can antagonize the antitumor effects of tamoxifen under some circumstances; however, soy isoflavones might have different effects when used at different doses. A relatively low in vitro concentration of soy isoflavones such as 1 microM/L seems to interfere with tamoxifen, whereas high in vitro concentrations such as those >10 microM/L might actually enhance tamoxifen effects. People on a high-soy diet have soy isoflavones levels ranging from 0.1-6 microM/L. Until more is known, advise patients taking tamoxifen to avoid therapeutic use of soy products.

Likelihood Possible Evidence B
Warfarin (Coumadin)

Theoretically, soy might interfere with the effects of warfarin.
Soy milk has been reported to decrease the international normalized ratio (INR) in a patient taking warfarin. The mechanism of this interaction is not known. However, animal and in vitro research suggests that soy may also inhibit platelet aggregation. Dosing adjustments for warfarin may be necessary.

Likelihood Possible Evidence D
Antibiotic Drugs

Theoretically, antibiotics may decrease the activity of soy isoflavones.
Intestinal bacteria are responsible in part for converting soy isoflavones into their active forms. Antibiotics may decrease the amount of intestinal bacteria and decrease its ability to convert isoflavones.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Substrates

Soy might modestly induce CYP2C9 enzymes. However, this effect does not seem to be clinically significant.
In vitro research suggests that an unhydrolyzed soy extract might induce CYP2C9. However, the significance of this interaction is likely minimal. In healthy females taking a specific extract of soy (Genistein Soy Complex, Source Naturals), blood levels of losartan, a CYP2C9 substrate, were not significantly affected.

Likelihood Unlikely Evidence D
Soy Isoflavones Extract, Powder full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Soy Isoflavones Extract, from the product label.

21st Century

See all 21st Century products
Name
21st Century HealthCare, Inc.
Street Address
2119 S. Wilson St.
City
Tempe
State
AZ
ZipCode
85282
Web Address
21stcenturyvitamins.com
Pharmacist Counseling Corner

Soy Isoflavones Extract by 21st Century: Common Questions

Does Soy Isoflavones Extract by 21st Century interact with any medications?
Yes. Based on its ingredients, Soy Isoflavones Extract has a known interaction with 611 medications, including 9 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Soy Isoflavones Extract contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
What are soy isoflavones?
Soy isoflavones are plant compounds naturally found in soy that act like estrogen in the body. This product gives you a concentrated dose of them in supplement form, rather than the amount you'd get from eating soy foods like tofu or soy milk.
Can I take this if I'm on blood pressure medication?
Maybe, but you need to check first — soy can lower blood pressure, so adding it to blood pressure drugs could drop your pressure too much. Run your specific medication through our checker on this page, then talk to your pharmacist to be sure.
What side effects should I watch for?
Most people tolerate soy well. Watch for bloating, constipation, diarrhea, or nausea — the most common issues. Some people can have allergic reactions like a rash or itching. Stop and talk to your doctor if anything worrisome develops.
Is this safe during pregnancy or breastfeeding?
There isn't enough safety data on concentrated isoflavone supplements in pregnancy or breastfeeding to know either way. Regular soy foods eaten normally while nursing are fine, but high-dose supplements haven't been well studied. Talk to your doctor or pharmacist for personalized advice.
Can this help my cholesterol?
The evidence suggests soy isoflavones are possibly effective for lowering cholesterol. Results vary, and it works best as part of a broader approach with diet and other lifestyle changes — not as a substitute for prescription cholesterol medication.
Does this product have any fillers?
Yes — it contains oat fiber, rice bran, cellulose, silicon dioxide, magnesium silicate, and magnesium stearate as inactive ingredients to form the capsule. If you have allergies or sensitivities to any of these, check the label.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Not sure if Soy Isoflavones Extract is safe with your meds?

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Soy Isoflavones Extract label
Go deeper

The Full Monographs Behind Soy Isoflavones Extract’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Soy

Interacts with 611 drugs

Soy is a nutritious bean that is a staple food and a popular source of plant protein and isoflavones. Eating soy foods as part of a balanced diet is generally considered safe for most people...

Read the full Soy monograph →
Sources

Sources & How We Checked

Soy Isoflavones Extract's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 88 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Soy 88 references
  1. Franke AA, Custer LJ, Tanaka Y. Isoflavones in human breast milk and other biological fluids. Am J Clin Nutr 1998;68:1466-73. PubMed
  2. Albertazzi P, Pansini F, Bonaccorsi G, et al. The effect of dietary soy supplementation on hot flushes. Obstet Gynecol 1998;91:6-11. PubMed
  3. Lu LJ, Anderson KE, Grady JJ, et al. Decreased ovarian hormones during a soya diet: implications for breast cancer prevention. Cancer Res 2000;60:4112-21.
  4. Pino AM, Valladares LE, Palma MA, et al. Dietary isoflavones affect sex hormone-binding globulin levels in postmenopausal women. J Clin Endocrinol Metab 2000;85:2797-800. DOI
  5. Nisley N, Klepser T. Phytoestrogens for the prevention and treatment of osteoporosis. Alt Med Alert 1999 Dec;138-42.
  6. McMichael-Phillips DF, Harding C, Morton M, et al. Effects of soy-protein supplementation on epithelial proliferation in the histologically normal human breast. Am J Clin Nutr 1998;68:1431S-5S. PubMed
  7. Petrakis NL, Barnes S, King EB, et al. Stimulatory influence of soy protein isolate on breast secretion in pre- and postmenopausal women. Cancer Epidemiol Biomarkers Prev 1996;5:785-94.
  8. Baird DD, Umbach DM, Lansdell L, et al. Dietary intervention study to assess estrogenicity of dietary soy among postmenopausal women. J Clin Endocrinol Metab 1995;80:1685-90. DOI
  9. Duncan AM, Underhill KE, Xu X, et al. Modest hormonal effects of soy isoflavones in postmenopausal women. J Clin Endocrinol Metab 1999;84:3479-84. PubMed
  10. Ginsburg J, Prelevic GM. Lack of significant hormonal effects and controlled trials of phyto-oestrogens. Lancet 2000;355:163-4. PubMed
  11. Anthony MS. Soy and cardiovascular disease: Cholesterol lowering and beyond. J Nutr 2000;130:662S-3S. PubMed
  12. Hargreaves DF, Potten CS, Harding C, et al. Two-week dietary soy supplementation has an estrogenic effect on normal premenopausal breast. J Clin Endocrinol Metab 1999;84:4017-24. DOI
  13. Lamartiniere CA. Protection against breast cancer with genistein: a component of soy. Am J Clin Nutr 2000;71:1705S-7S. PubMed
  14. Electronic Code of Federal Regulations. Title 21. Part 182 -- Substances Generally Recognized As Safe. Available at: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=182
  15. Codina R, Ardusso L, Lockey RF, et al. Sensitization to soybean hull allergens in subjects exposed to different levels of soybean dust inhalation in Argentina. J Allergy Clin Immunol 2000;105:570-6. PubMed
  16. Anto JM, Sunyer J, Rodriguez-Roisin R, et al. Community outbreaks of asthma associated with inhalation of soybean dust. Toxicoepidemiological Committee. N Engl J Med 1989;320:1097-1102. PubMed
  17. White MC, Etzel RA, Olson DR, Goldstein IF. Re-examination of epidemic asthma in New Orleans, Louisianna, in relation to the presence of soy at the harbor. Am J Epidemiol 1997;145:432-8.
  18. Murkies A, Dalais FS, Briganti EM, et al. Phytoestrogens and breast cancer in postmenopausal women: a case control study. Menopause 2000;7:289-96. PubMed
  19. Setchell KD, Cassidy A. Dietary isoflavones: biological effects and relevance to human health. J Nutr 1999;129:758S-67S. PubMed
  20. Teixeira SR, Potter SM, Weigel R, et al. Effects of feeding 4 levels of soy protein for 3 and 6 wk on blood lipids and apolipoproteins in moderately hypercholesterolemic men. Am J Clin Nutr 2000;71:1077-84. PubMed
  21. White LR, Petrovitch H, Ross GW, et al. Brain aging and midlife tofu consumption. J Am Coll Nutr 2000;19:242-55. PubMed
  22. Grodstein F, Mayeux R, Stampfer MJ. Tofu and cognitive function: food for thought. J Am Coll Nutr 2000;19:207-9. PubMed
  23. Divi RL, Chang HC, Doerge DR. Anti-thyroid isoflavones from soybean: isolation, characterization, and mechanisms of action. Biochem Pharmacol 1997;54:1087-96. PubMed
  24. de Lemos ML. Effects of soy phytoestrogens genistein and daidzein on breast cancer growth. Ann Pharmacother 2001;35:1118-21. PubMed
  25. Strom BL, Schinnar R, Ziegler EE, et al. Exposure to soy-based formula in infancy and endocrinological and reproductive outcomes in young adulthood. JAMA 2001;286:807-14. PubMed
  26. Goodman MT, Wilkens LR, Hankin JH, et al. Association of soy and fiber consumption with the risk of endometrial cancer. Am J Epidemiol 1997;146:294-306. PubMed
  27. Wu AH, Yang D, Pike MC. A meta-analysis of soyfoods and risk of stomach cancer: the problem of potential confounders. Cancer Epidemiol Biomarkers Prev 2000;9:1051-8.
  28. Ji BT, Chow WH, Yang G, et al. Correspondence re: AH Wu et al, A meta-analysis of soyfoods and risk of stomach cancer: the problem of potential confounders. Cancer Epidemiol Biomarkers Prev 2001;10:570.
  29. Foth D, Cline JM. Effects of mammalian and plant estrogens on mammary glands and uteri of macaques. Am J Clin Nutr 1998;68:1413S-7S. PubMed
  30. Duncan AM, Merz BE, Xu X, et al. Soy isoflavones exert modest hormonal effects in premenopausal women. J Clin Endocrinol Metab 1999;84:192-7. DOI
  31. Morito K, Hirose T, Kinjo J, et al. Interaction of phytoestrogens with estrogen receptors alpha and beta. Biol Pharm Bull 2001;24:351-6. PubMed
  32. Persky VW, Turyk ME, Wang L, et al. Effect of soy protein on endogenous hormones in postmenopausal women. Am J Clin Nutr 2002;75:145-53. PubMed
  33. Ju YH, Doerge DR, Allred KF, et al. Dietary Genistein Negates the Inhibitory Effect of Tamoxifen on Growth of Estrogen-dependent Human Breast Cancer (MCF-7) Cells Implanted in Athymic Mice. Cancer Res 2002;62:2474-7 .
  34. Cambria-Kiely JA. Effect of soy milk on warfarin efficacy. Ann Pharmacother 2002;36:1893-6.. PubMed
  35. Ziegler RG, Hoover RN, Pike MC, et al. Migration patterns and breast cancer risk in Asian-American women. J Natl Cancer Inst 1993;85:1819-27.. PubMed
  36. Brown BD, Thomas W, Hutchins A, et al. Types of dietary fat and soy minimally affect hormones and biomarkers associated with breast cancer risk in premenopausal women. Nutr Cancer 2002;43:22-30.. PubMed
  37. Sun CL, Yuan JM, Arakawa K, et al. Dietary soy and increased risk of bladder cancer: the Singapore Chinese Health Study. Cancer Epidemiol Biomarkers Prev 2002;11:1674-7.
  38. Balk JL, Whiteside DA, Naus G, et al. A pilot study of the effects of phytoestrogen supplementation on postmenopausal endometrium. J Soc Gynecol Investig 2002;9:238-42.. DOI
  39. Horn-Ross PL, John EM, Canchola AJ, et al. Phytoestrogen intake and endometrial cancer risk. J Natl Cancer Inst 2003;95:1158-64.. PubMed
  40. Kumar NB, Cantor A, Allen K et al. The specific role of isoflavones in reducing prostate cancer risk. Prostate 2004;59:141-7. PubMed
  41. Chen A, Rogan WJ. Isoflavones in soy infant formula: a review of evidence for endocrine and other activity in infants. Annu Rev Nutr 2004;24:33-54. PubMed
  42. Chen YM, Ho SC, Lam SS, et al. Soy isoflavones have a favorable effect on bone loss in Chinese postmenopausal women with lower bone mass: a double-blind, randomized, controlled trial. J Clin Endocrinol Metab 2003;88:4740-7. PubMed
  43. Unfer V, Casini ML, Costabile L, et al. Endometrial effects of long-term treatment with phytoestrogens: a randomized, double-blind, placebo-controlled study. Fertil Steril 2004;82:145-8. PubMed
  44. Bruce B, Messina M, Spiller G. Isoflavone supplements do not affect thyroid function in iodine-replete postmemopausal women. J Med Food 2003;6:309-16.
  45. He J, Gu D, Wu X, et al. Effect of soybean protein on blood pressure: A randomized, controlled trial. Ann Intern Med 2005;143:1-9. PubMed
  46. Kaari C, Haidar MA, Junior JMS, et al. Randomized clinical trial comparing conjugated equine estrogens and isoflavones in postmenopausal women: a pilot study. Maturitas 2006;53:49-58. PubMed
  47. Sacks FM, Lichtenstein A, Van Horn L, et al. Soy protein, isoflavones, and cardiovascular health. An American Heart Association Science Advisory for Professionals from the Nutrition Committee. Circulation 2006;113:1034-44. PubMed
  48. Jones JL, Daley BJ, Enderson BL, et al. Genistein inhibits tamoxifen effects on cell proliferation and cell cycle arrest in T47D breast cancer cells. Am Surg 2002;68:575-7. DOI
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DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

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